linux-kernel - Re: [PATCH] Reduce vm_stat cacheline contention in __vm_enough

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Message-ID: <alpine.DEB.2.00.1110131602020.26553@router.home>
Date:	Thu, 13 Oct 2011 16:02:58 -0500 (CDT)
From:	Christoph Lameter <cl@...two.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Dimitri Sivanich <sivanich@....com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Mel Gorman <mel@....ul.ie>
Subject: Re: [PATCH] Reduce vm_stat cacheline contention in
 __vm_enough_memory

On Thu, 13 Oct 2011, Andrew Morton wrote:

> > If there are no updates occurring for a while (due to increased deltas
> > and/or vmstat updates) then the vm_stat cacheline should be able to stay
> > in shared mode in multiple processors and the performance should increase.
> >
>
> We could cacheline align vm_stat[].  But the thing is pretty small - we
> couild put each entry in its own cacheline.

Which in turn would increase the cache footprint of some key kernel
functions (because they need multiple vm_stat entries) and cause eviction
of other cachelines that then reduce overall system performance again.

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